src/lists.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use std::cmp;
  12 use std::iter::Peekable;
  13
  14 use syntax::codemap::{self, CodeMap, BytePos};
  15
  16 use {Indent, Shape};
  17 use comment::{FindUncommented, rewrite_comment, find_comment_end};
  18 use config::{Config, IndentStyle};
  19 use rewrite::RewriteContext;
  20
  21 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
  22 /// Formatting tactic for lists. This will be cast down to a
  23 /// DefinitiveListTactic depending on the number and length of the items and
  24 /// their comments.
  25 pub enum ListTactic {
  26     // One item per row.
  27     Vertical,
  28     // All items on one row.
  29     Horizontal,
  30     // Try Horizontal layout, if that fails then vertical.
  31     HorizontalVertical,
  32     // HorizontalVertical with a soft limit of n characters.
  33     LimitedHorizontalVertical(usize),
  34     // Pack as many items as possible per row over (possibly) many rows.
  35     Mixed,
  36 }
  37
  38 impl_enum_serialize_and_deserialize!(ListTactic, Vertical, Horizontal, HorizontalVertical, Mixed);
  39
  40 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
  41 pub enum SeparatorTactic {
  42     Always,
  43     Never,
  44     Vertical,
  45 }
  46
  47 impl_enum_serialize_and_deserialize!(SeparatorTactic, Always, Never, Vertical);
  48
  49 impl SeparatorTactic {
  50     pub fn from_bool(b: bool) -> SeparatorTactic {
  51         if b {
  52             SeparatorTactic::Always
  53         } else {
  54             SeparatorTactic::Never
  55         }
  56     }
  57 }
  58
  59 pub struct ListFormatting<'a> {
  60     pub tactic: DefinitiveListTactic,
  61     pub separator: &'a str,
  62     pub trailing_separator: SeparatorTactic,
  63     pub shape: Shape,
  64     // Non-expressions, e.g. items, will have a new line at the end of the list.
  65     // Important for comment styles.
  66     pub ends_with_newline: bool,
  67     pub config: &'a Config,
  68 }
  69
  70 pub fn format_fn_args<I>(items: I, shape: Shape, config: &Config) -> Option<String>
  71     where I: Iterator<Item = ListItem>
  72 {
  73     list_helper(items,
  74                 shape,
  75                 config,
  76                 ListTactic::LimitedHorizontalVertical(config.fn_call_width()))
  77 }
  78
  79 pub fn format_item_list<I>(items: I, shape: Shape, config: &Config) -> Option<String>
  80     where I: Iterator<Item = ListItem>
  81 {
  82     list_helper(items, shape, config, ListTactic::HorizontalVertical)
  83 }
  84
  85 pub fn list_helper<I>(items: I, shape: Shape, config: &Config, tactic: ListTactic) -> Option<String>
  86     where I: Iterator<Item = ListItem>
  87 {
  88     let item_vec: Vec<_> = items.collect();
  89     let tactic = definitive_tactic(&item_vec, tactic, shape.width);
  90     let fmt = ListFormatting {
  91         tactic: tactic,
  92         separator: ",",
  93         trailing_separator: SeparatorTactic::Never,
  94         shape: shape,
  95         ends_with_newline: false,
  96         config: config,
  97     };
  98
  99     write_list(&item_vec, &fmt)
 100 }
 101
 102 impl AsRef<ListItem> for ListItem {
 103     fn as_ref(&self) -> &ListItem {
 104         self
 105     }
 106 }
 107
 108 pub struct ListItem {
 109     // None for comments mean that they are not present.
 110     pub pre_comment: Option<String>,
 111     // Item should include attributes and doc comments. None indicates a failed
 112     // rewrite.
 113     pub item: Option<String>,
 114     pub post_comment: Option<String>,
 115     // Whether there is extra whitespace before this item.
 116     pub new_lines: bool,
 117 }
 118
 119 impl ListItem {
 120     pub fn is_multiline(&self) -> bool {
 121         self.item.as_ref().map_or(false, |s| s.contains('\n')) || self.pre_comment.is_some() ||
 122         self.post_comment
 123             .as_ref()
 124             .map_or(false, |s| s.contains('\n'))
 125     }
 126
 127     pub fn has_line_pre_comment(&self) -> bool {
 128         self.pre_comment
 129             .as_ref()
 130             .map_or(false, |comment| comment.starts_with("//"))
 131     }
 132
 133     pub fn from_str<S: Into<String>>(s: S) -> ListItem {
 134         ListItem {
 135             pre_comment: None,
 136             item: Some(s.into()),
 137             post_comment: None,
 138             new_lines: false,
 139         }
 140     }
 141 }
 142
 143 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
 144 /// The definitive formatting tactic for lists.
 145 pub enum DefinitiveListTactic {
 146     Vertical,
 147     Horizontal,
 148     Mixed,
 149 }
 150
 151 pub fn definitive_tactic<I, T>(items: I, tactic: ListTactic, width: usize) -> DefinitiveListTactic
 152     where I: IntoIterator<Item = T> + Clone,
 153           T: AsRef<ListItem>
 154 {
 155     let pre_line_comments = items
 156         .clone()
 157         .into_iter()
 158         .any(|item| item.as_ref().has_line_pre_comment());
 159
 160     let limit = match tactic {
 161         _ if pre_line_comments => return DefinitiveListTactic::Vertical,
 162         ListTactic::Mixed => return DefinitiveListTactic::Mixed,
 163         ListTactic::Horizontal => return DefinitiveListTactic::Horizontal,
 164         ListTactic::Vertical => return DefinitiveListTactic::Vertical,
 165         ListTactic::LimitedHorizontalVertical(limit) => ::std::cmp::min(width, limit),
 166         ListTactic::HorizontalVertical => width,
 167     };
 168
 169     let (sep_count, total_width) = calculate_width(items.clone());
 170     let sep_len = ", ".len(); // FIXME: make more generic?
 171     let total_sep_len = sep_len * sep_count.checked_sub(1).unwrap_or(0);
 172     let real_total = total_width + total_sep_len;
 173
 174     if real_total <= limit && !pre_line_comments &&
 175        !items.into_iter().any(|item| item.as_ref().is_multiline()) {
 176         DefinitiveListTactic::Horizontal
 177     } else {
 178         DefinitiveListTactic::Vertical
 179     }
 180 }
 181
 182 // Format a list of commented items into a string.
 183 // TODO: add unit tests
 184 pub fn write_list<I, T>(items: I, formatting: &ListFormatting) -> Option<String>
 185     where I: IntoIterator<Item = T>,
 186           T: AsRef<ListItem>
 187 {
 188     let tactic = formatting.tactic;
 189     let sep_len = formatting.separator.len();
 190
 191     // Now that we know how we will layout, we can decide for sure if there
 192     // will be a trailing separator.
 193     let trailing_separator = needs_trailing_separator(formatting.trailing_separator, tactic);
 194     let mut result = String::new();
 195     let mut iter = items.into_iter().enumerate().peekable();
 196
 197     let mut line_len = 0;
 198     let indent_str = &formatting.shape.indent.to_string(formatting.config);
 199     while let Some((i, item)) = iter.next() {
 200         let item = item.as_ref();
 201         let inner_item = try_opt!(item.item.as_ref());
 202         let first = i == 0;
 203         let last = iter.peek().is_none();
 204         let separate = !last || trailing_separator;
 205         let item_sep_len = if separate { sep_len } else { 0 };
 206
 207         // Item string may be multi-line. Its length (used for block comment alignment)
 208         // should be only the length of the last line.
 209         let item_last_line = if item.is_multiline() {
 210             inner_item.lines().last().unwrap_or("")
 211         } else {
 212             inner_item.as_ref()
 213         };
 214         let mut item_last_line_width = item_last_line.len() + item_sep_len;
 215         if item_last_line.starts_with(indent_str) {
 216             item_last_line_width -= indent_str.len();
 217         }
 218
 219         match tactic {
 220             DefinitiveListTactic::Horizontal if !first => {
 221                 result.push(' ');
 222             }
 223             DefinitiveListTactic::Vertical if !first => {
 224                 result.push('\n');
 225                 result.push_str(indent_str);
 226             }
 227             DefinitiveListTactic::Mixed => {
 228                 let total_width = total_item_width(item) + item_sep_len;
 229
 230                 // 1 is space between separator and item.
 231                 if line_len > 0 && line_len + 1 + total_width > formatting.shape.width {
 232                     result.push('\n');
 233                     result.push_str(indent_str);
 234                     line_len = 0;
 235                 }
 236
 237                 if line_len > 0 {
 238                     result.push(' ');
 239                     line_len += 1;
 240                 }
 241
 242                 line_len += total_width;
 243             }
 244             _ => {}
 245         }
 246
 247         // Pre-comments
 248         if let Some(ref comment) = item.pre_comment {
 249             // Block style in non-vertical mode.
 250             let block_mode = tactic != DefinitiveListTactic::Vertical;
 251             // Width restriction is only relevant in vertical mode.
 252             let comment =
 253                 try_opt!(rewrite_comment(comment, block_mode, formatting.shape, formatting.config));
 254             result.push_str(&comment);
 255
 256             if tactic == DefinitiveListTactic::Vertical {
 257                 result.push('\n');
 258                 result.push_str(indent_str);
 259             } else {
 260                 result.push(' ');
 261             }
 262         }
 263
 264         result.push_str(&inner_item[..]);
 265
 266         // Post-comments
 267         if tactic != DefinitiveListTactic::Vertical && item.post_comment.is_some() {
 268             let comment = item.post_comment.as_ref().unwrap();
 269             let formatted_comment =
 270                 try_opt!(rewrite_comment(comment,
 271                                          true,
 272                                          Shape::legacy(formatting.shape.width, Indent::empty()),
 273                                          formatting.config));
 274
 275             result.push(' ');
 276             result.push_str(&formatted_comment);
 277         }
 278
 279         if separate {
 280             result.push_str(formatting.separator);
 281         }
 282
 283         if tactic == DefinitiveListTactic::Vertical && item.post_comment.is_some() {
 284             // 1 = space between item and comment.
 285             let width = formatting
 286                 .shape
 287                 .width
 288                 .checked_sub(item_last_line_width + 1)
 289                 .unwrap_or(1);
 290             let mut offset = formatting.shape.indent;
 291             offset.alignment += item_last_line_width + 1;
 292             let comment = item.post_comment.as_ref().unwrap();
 293
 294             debug!("Width = {}, offset = {:?}", width, offset);
 295             // Use block-style only for the last item or multiline comments.
 296             let block_style = !formatting.ends_with_newline && last ||
 297                               comment.trim().contains('\n') ||
 298                               comment.trim().len() > width;
 299
 300             let formatted_comment = try_opt!(rewrite_comment(comment,
 301                                                              block_style,
 302                                                              Shape::legacy(width, offset),
 303                                                              formatting.config));
 304
 305             if !formatted_comment.starts_with('\n') {
 306                 result.push(' ');
 307             }
 308             result.push_str(&formatted_comment);
 309         }
 310
 311         if !last && tactic == DefinitiveListTactic::Vertical && item.new_lines {
 312             result.push('\n');
 313         }
 314     }
 315
 316     Some(result)
 317 }
 318
 319 pub struct ListItems<'a, I, F1, F2, F3>
 320     where I: Iterator
 321 {
 322     codemap: &'a CodeMap,
 323     inner: Peekable<I>,
 324     get_lo: F1,
 325     get_hi: F2,
 326     get_item_string: F3,
 327     prev_span_end: BytePos,
 328     next_span_start: BytePos,
 329     terminator: &'a str,
 330 }
 331
 332 impl<'a, T, I, F1, F2, F3> Iterator for ListItems<'a, I, F1, F2, F3>
 333     where I: Iterator<Item = T>,
 334           F1: Fn(&T) -> BytePos,
 335           F2: Fn(&T) -> BytePos,
 336           F3: Fn(&T) -> Option<String>
 337 {
 338     type Item = ListItem;
 339
 340     fn next(&mut self) -> Option<Self::Item> {
 341         let white_space: &[_] = &[' ', '\t'];
 342
 343         self.inner.next().map(|item| {
 344             let mut new_lines = false;
 345             // Pre-comment
 346             let pre_snippet = self.codemap
 347                 .span_to_snippet(codemap::mk_sp(self.prev_span_end, (self.get_lo)(&item)))
 348                 .unwrap();
 349             let trimmed_pre_snippet = pre_snippet.trim();
 350             let has_pre_comment = trimmed_pre_snippet.contains("//") ||
 351                                   trimmed_pre_snippet.contains("/*");
 352             let pre_comment = if has_pre_comment {
 353                 Some(trimmed_pre_snippet.to_owned())
 354             } else {
 355                 None
 356             };
 357
 358             // Post-comment
 359             let next_start = match self.inner.peek() {
 360                 Some(next_item) => (self.get_lo)(next_item),
 361                 None => self.next_span_start,
 362             };
 363             let post_snippet = self.codemap
 364                 .span_to_snippet(codemap::mk_sp((self.get_hi)(&item), next_start))
 365                 .unwrap();
 366
 367             let comment_end = match self.inner.peek() {
 368                 Some(..) => {
 369                     let mut block_open_index = post_snippet.find("/*");
 370                     // check if it realy is a block comment (and not //*)
 371                     if let Some(i) = block_open_index {
 372                         if i > 0 && &post_snippet[i - 1..i] == "/" {
 373                             block_open_index = None;
 374                         }
 375                     }
 376                     let newline_index = post_snippet.find('\n');
 377                     let separator_index = post_snippet.find_uncommented(",").unwrap();
 378
 379                     match (block_open_index, newline_index) {
 380                         // Separator before comment, with the next item on same line.
 381                         // Comment belongs to next item.
 382                         (Some(i), None) if i > separator_index => separator_index + 1,
 383                         // Block-style post-comment before the separator.
 384                         (Some(i), None) => {
 385                             cmp::max(find_comment_end(&post_snippet[i..]).unwrap() + i,
 386                                      separator_index + 1)
 387                         }
 388                         // Block-style post-comment. Either before or after the separator.
 389                         (Some(i), Some(j)) if i < j => {
 390                             cmp::max(find_comment_end(&post_snippet[i..]).unwrap() + i,
 391                                      separator_index + 1)
 392                         }
 393                         // Potential *single* line comment.
 394                         (_, Some(j)) if j > separator_index => j + 1,
 395                         _ => post_snippet.len(),
 396                     }
 397                 }
 398                 None => {
 399                     post_snippet
 400                         .find_uncommented(self.terminator)
 401                         .unwrap_or(post_snippet.len())
 402                 }
 403             };
 404
 405             if !post_snippet.is_empty() && comment_end > 0 {
 406                 // Account for extra whitespace between items. This is fiddly
 407                 // because of the way we divide pre- and post- comments.
 408
 409                 // Everything from the separator to the next item.
 410                 let test_snippet = &post_snippet[comment_end - 1..];
 411                 let first_newline = test_snippet.find('\n').unwrap_or(test_snippet.len());
 412                 // From the end of the first line of comments.
 413                 let test_snippet = &test_snippet[first_newline..];
 414                 let first = test_snippet
 415                     .find(|c: char| !c.is_whitespace())
 416                     .unwrap_or(test_snippet.len());
 417                 // From the end of the first line of comments to the next non-whitespace char.
 418                 let test_snippet = &test_snippet[..first];
 419
 420                 if test_snippet.chars().filter(|c| c == &'\n').count() > 1 {
 421                     // There were multiple line breaks which got trimmed to nothing.
 422                     new_lines = true;
 423                 }
 424             }
 425
 426             // Cleanup post-comment: strip separators and whitespace.
 427             self.prev_span_end = (self.get_hi)(&item) + BytePos(comment_end as u32);
 428             let post_snippet = post_snippet[..comment_end].trim();
 429
 430             let post_snippet_trimmed = if post_snippet.starts_with(',') {
 431                 post_snippet[1..].trim_matches(white_space)
 432             } else if post_snippet.ends_with(',') {
 433                 post_snippet[..(post_snippet.len() - 1)].trim_matches(white_space)
 434             } else {
 435                 post_snippet
 436             };
 437
 438             let post_comment = if !post_snippet_trimmed.is_empty() {
 439                 Some(post_snippet_trimmed.to_owned())
 440             } else {
 441                 None
 442             };
 443
 444             ListItem {
 445                 pre_comment: pre_comment,
 446                 item: (self.get_item_string)(&item),
 447                 post_comment: post_comment,
 448                 new_lines: new_lines,
 449             }
 450         })
 451     }
 452 }
 453
 454 // Creates an iterator over a list's items with associated comments.
 455 pub fn itemize_list<'a, T, I, F1, F2, F3>(codemap: &'a CodeMap,
 456                                           inner: I,
 457                                           terminator: &'a str,
 458                                           get_lo: F1,
 459                                           get_hi: F2,
 460                                           get_item_string: F3,
 461                                           prev_span_end: BytePos,
 462                                           next_span_start: BytePos)
 463                                           -> ListItems<'a, I, F1, F2, F3>
 464     where I: Iterator<Item = T>,
 465           F1: Fn(&T) -> BytePos,
 466           F2: Fn(&T) -> BytePos,
 467           F3: Fn(&T) -> Option<String>
 468 {
 469     ListItems {
 470         codemap: codemap,
 471         inner: inner.peekable(),
 472         get_lo: get_lo,
 473         get_hi: get_hi,
 474         get_item_string: get_item_string,
 475         prev_span_end: prev_span_end,
 476         next_span_start: next_span_start,
 477         terminator: terminator,
 478     }
 479 }
 480
 481 fn needs_trailing_separator(separator_tactic: SeparatorTactic,
 482                             list_tactic: DefinitiveListTactic)
 483                             -> bool {
 484     match separator_tactic {
 485         SeparatorTactic::Always => true,
 486         SeparatorTactic::Vertical => list_tactic == DefinitiveListTactic::Vertical,
 487         SeparatorTactic::Never => false,
 488     }
 489 }
 490
 491 /// Returns the count and total width of the list items.
 492 fn calculate_width<I, T>(items: I) -> (usize, usize)
 493     where I: IntoIterator<Item = T>,
 494           T: AsRef<ListItem>
 495 {
 496     items
 497         .into_iter()
 498         .map(|item| total_item_width(item.as_ref()))
 499         .fold((0, 0), |acc, l| (acc.0 + 1, acc.1 + l))
 500 }
 501
 502 fn total_item_width(item: &ListItem) -> usize {
 503     comment_len(item.pre_comment.as_ref().map(|x| &(*x)[..])) +
 504     comment_len(item.post_comment.as_ref().map(|x| &(*x)[..])) +
 505     item.item.as_ref().map_or(0, |str| str.len())
 506 }
 507
 508 fn comment_len(comment: Option<&str>) -> usize {
 509     match comment {
 510         Some(s) => {
 511             let text_len = s.trim().len();
 512             if text_len > 0 {
 513                 // We'll put " /*" before and " */" after inline comments.
 514                 text_len + 6
 515             } else {
 516                 text_len
 517             }
 518         }
 519         None => 0,
 520     }
 521 }
 522
 523 // Compute horizontal and vertical shapes for a struct-lit-like thing.
 524 pub fn struct_lit_shape(shape: Shape,
 525                         context: &RewriteContext,
 526                         prefix_width: usize,
 527                         suffix_width: usize)
 528                         -> Option<(Option<Shape>, Shape)> {
 529     let v_shape = match context.config.struct_lit_style() {
 530         IndentStyle::Visual => {
 531             try_opt!(try_opt!(shape.shrink_left(prefix_width)).sub_width(suffix_width))
 532         }
 533         IndentStyle::Block => {
 534             let shape = shape.block_indent(context.config.tab_spaces());
 535             Shape {
 536                 width: try_opt!(context.config.max_width().checked_sub(shape.indent.width())),
 537                 ..shape
 538             }
 539         }
 540     };
 541     let h_shape = shape.sub_width(prefix_width + suffix_width);
 542     Some((h_shape, v_shape))
 543 }
 544
 545 // Compute the tactic for the internals of a struct-lit-like thing.
 546 pub fn struct_lit_tactic(h_shape: Option<Shape>,
 547                          context: &RewriteContext,
 548                          items: &[ListItem])
 549                          -> DefinitiveListTactic {
 550     if let Some(h_shape) = h_shape {
 551         let mut prelim_tactic = match (context.config.struct_lit_style(), items.len()) {
 552             (IndentStyle::Visual, 1) => ListTactic::HorizontalVertical,
 553             _ => context.config.struct_lit_multiline_style().to_list_tactic(),
 554         };
 555
 556         if prelim_tactic == ListTactic::HorizontalVertical && items.len() > 1 {
 557             prelim_tactic =
 558                 ListTactic::LimitedHorizontalVertical(context.config.struct_lit_width());
 559         }
 560
 561         definitive_tactic(items, prelim_tactic, h_shape.width)
 562     } else {
 563         DefinitiveListTactic::Vertical
 564     }
 565 }
 566
 567 // Given a tactic and possible shapes for horizontal and vertical layout,
 568 // come up with the actual shape to use.
 569 pub fn shape_for_tactic(tactic: DefinitiveListTactic,
 570                         h_shape: Option<Shape>,
 571                         v_shape: Shape)
 572                         -> Shape {
 573     match tactic {
 574         DefinitiveListTactic::Horizontal => h_shape.unwrap(),
 575         _ => v_shape,
 576     }
 577 }
 578
 579 // Create a ListFormatting object for formatting the internals of a
 580 // struct-lit-like thing, that is a series of fields.
 581 pub fn struct_lit_formatting<'a>(shape: Shape,
 582                                  tactic: DefinitiveListTactic,
 583                                  context: &'a RewriteContext,
 584                                  force_no_trailing_comma: bool)
 585                                  -> ListFormatting<'a> {
 586     let ends_with_newline = context.config.struct_lit_style() != IndentStyle::Visual &&
 587                             tactic == DefinitiveListTactic::Vertical;
 588     ListFormatting {
 589         tactic: tactic,
 590         separator: ",",
 591         trailing_separator: if force_no_trailing_comma {
 592             SeparatorTactic::Never
 593         } else {
 594             context.config.trailing_comma()
 595         },
 596         shape: shape,
 597         ends_with_newline: ends_with_newline,
 598         config: context.config,
 599     }
 600 }